From 34ebccddcd234df7b4f25d6dd6355a886c831edb Mon Sep 17 00:00:00 2001
From: Greg Stark <stark@mit.edu>
Date: Mon, 15 Feb 2010 02:36:26 +0000
Subject: [PATCH] Display explain buffers measurements in memory units rather
than blocks. Also show "Total Buffer Usage" to hint that these are totals not
averages per loop
---
src/backend/commands/explain.c | 98 +++++++++++++++++++++++++---------
1 file changed, 74 insertions(+), 24 deletions(-)
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 8c9b060e6bd..38ccc845854 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -7,7 +7,7 @@
* Portions Copyright (c) 1994-5, Regents of the University of California
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/commands/explain.c,v 1.200 2010/02/01 15:43:35 rhaas Exp $
+ * $PostgreSQL: pgsql/src/backend/commands/explain.c,v 1.201 2010/02/15 02:36:26 stark Exp $
*
*-------------------------------------------------------------------------
*/
@@ -98,6 +98,7 @@ static void ExplainJSONLineEnding(ExplainState *es);
static void ExplainYAMLLineStarting(ExplainState *es);
static void escape_json(StringInfo buf, const char *str);
static void escape_yaml(StringInfo buf, const char *str);
+static double normalize_memory(double amount, char **unit, int *precision);
/*
@@ -1081,47 +1082,63 @@ ExplainNode(Plan *plan, PlanState *planstate,
if (has_shared || has_local || has_temp)
{
appendStringInfoSpaces(es->str, es->indent * 2);
- appendStringInfoString(es->str, "Buffers:");
+ appendStringInfoString(es->str, "Total Buffer Usage:");
if (has_shared)
{
+ char *hit_unit, *read_unit, *written_unit;
+ int hit_prec, read_prec, written_prec;
+ double hit_mem = normalize_memory((double)usage->shared_blks_hit * BLCKSZ, &hit_unit, &hit_prec);
+ double read_mem = normalize_memory((double)usage->shared_blks_read * BLCKSZ, &read_unit, &read_prec);
+ double written_mem = normalize_memory((double)usage->shared_blks_written * BLCKSZ, &written_unit, &written_prec);
+
appendStringInfoString(es->str, " shared");
- if (usage->shared_blks_hit > 0)
- appendStringInfo(es->str, " hit=%ld",
- usage->shared_blks_hit);
+ appendStringInfo(es->str, " hit=%.*f%s",
+ hit_prec, hit_mem, hit_unit);
if (usage->shared_blks_read > 0)
- appendStringInfo(es->str, " read=%ld",
- usage->shared_blks_read);
+ appendStringInfo(es->str, " read=%.*f%s",
+ read_prec, read_mem, read_unit);
if (usage->shared_blks_written > 0)
- appendStringInfo(es->str, " written=%ld",
- usage->shared_blks_written);
+ appendStringInfo(es->str, " written=%.*f%s",
+ written_prec, written_mem, written_unit);
if (has_local || has_temp)
appendStringInfoChar(es->str, ',');
}
if (has_local)
{
- appendStringInfoString(es->str, " local");
- if (usage->local_blks_hit > 0)
- appendStringInfo(es->str, " hit=%ld",
- usage->local_blks_hit);
- if (usage->local_blks_read > 0)
- appendStringInfo(es->str, " read=%ld",
- usage->local_blks_read);
- if (usage->local_blks_written > 0)
- appendStringInfo(es->str, " written=%ld",
- usage->local_blks_written);
+ char *hit_unit, *read_unit, *written_unit;
+ int hit_prec, read_prec, written_prec;
+ double hit_mem = normalize_memory((double)usage->local_blks_hit * BLCKSZ, &hit_unit, &hit_prec);
+ double read_mem = normalize_memory((double)usage->local_blks_read * BLCKSZ, &read_unit, &read_prec);
+ double written_mem = normalize_memory((double)usage->local_blks_written * BLCKSZ, &written_unit, &written_prec);
+
+ appendStringInfoString(es->str, " local");
+ if (usage->local_blks_hit > 0)
+ appendStringInfo(es->str, " hit=%.*f%s",
+ hit_prec, hit_mem, hit_unit);
+ if (usage->local_blks_read > 0)
+ appendStringInfo(es->str, " read=%.*f%s",
+ read_prec, read_mem, read_unit);
+ if (usage->local_blks_written > 0)
+ appendStringInfo(es->str, " written=%.*f%s",
+ written_prec, written_mem, written_unit);
if (has_temp)
appendStringInfoChar(es->str, ',');
}
if (has_temp)
{
+ char *read_unit, *written_unit;
+ int read_prec, written_prec;
+ double read_mem = normalize_memory((double)usage->temp_blks_read * BLCKSZ, &read_unit, &read_prec);
+ double written_mem = normalize_memory((double)usage->temp_blks_written * BLCKSZ, &written_unit, &written_prec);
+
appendStringInfoString(es->str, " temp");
if (usage->temp_blks_read > 0)
- appendStringInfo(es->str, " read=%ld",
- usage->temp_blks_read);
- if (usage->temp_blks_written > 0)
- appendStringInfo(es->str, " written=%ld",
- usage->temp_blks_written);
+ appendStringInfo(es->str, " read=%.*f%s",
+ read_prec, read_mem, read_unit);
+ if (usage->temp_blks_written > 0)
+ appendStringInfo(es->str, " written=%.*f%s",
+ written_prec, written_mem, written_unit);
}
appendStringInfoChar(es->str, '\n');
}
@@ -2153,3 +2170,36 @@ escape_yaml(StringInfo buf, const char *str)
appendStringInfo(buf, "%s", str);
}
+
+/*
+ * For a quantity of bytes pick a reasonable display unit for it and
+ * return the quantity in that unit. Also return the unit name and a
+ * reasonable precision via the reference parameters.
+ */
+
+static double normalize_memory(double amount, char **unit, int *precision)
+{
+ static char *units[] = {"bytes", "kB", "MB", "GB", "TB", "PB"};
+ char **u = units, **last = units + (sizeof(units)/sizeof(*units)-1);
+
+ while (amount > 1024.0 && u < last)
+ {
+ amount /= 1024.0;
+ u += 1;
+ }
+
+ *unit = *u;
+
+ /* if it's bytes or kB then don't print decimals since that's less
+ * than blocksize, otherwise always print 3 significant digits */
+ if (u == units || u == units+1 )
+ *precision = 0;
+ else if (amount < 10)
+ *precision = 2;
+ else if (amount < 100)
+ *precision = 1;
+ else
+ *precision = 0;
+
+ return amount;
+}
--
GitLab